Embedded microelectromechanical systems sensor and related devices and methods

ABSTRACT

Embodiments of embedded MEMS sensors and related methods are described herein. Other embodiments and related methods are also disclosed herein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT Application Ser. No.PCT/US2009/068528, filed Dec. 17, 2009, which claims the benefit of: (1)U.S. Provisional Application Ser. No. 61/147,683, filed on Jan. 27,2009; (2) U.S. Provisional Application Ser. No. 61/174,438, filed onApr. 30, 2009; and (3) U.S. Provisional Application Ser. No. 61/222,451,filed on Jul. 1, 2009. PCT Application Serial No. PCT/US2009/068528,U.S. Provisional Application Ser. No. 61/147,683, U.S. ProvisionalApplication Ser. No. 61/174,438, and U.S. Provisional Application Ser.No. 61/222,451 are incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

At least part of the disclosure herein was funded with governmentsupport under grant/contract number W911NF-04-2-0005, awarded by theArmy Research Laboratory (ARL). The United States Government may havecertain rights in this application.

FIELD OF THE INVENTION

The disclosure herein relates generally to semiconductor devices andmethods of providing semiconductor devices, and relates, moreparticularly, to semiconductor devices for displays with embedded MEMS(Micro Electro Mechanical System) sensors and related methods.

DESCRIPTION OF THE BACKGROUND

In the electronics industry, flexible substrates are quickly becomingpopular as a base for electronic circuits. Flexible substrates caninclude a wide variety of materials including, for example, any of amyriad of plastics. Once a desired electronic component, circuit, orcircuits are formed over a surface of the flexible substrate, theflexible substrate can be attached to a final product or incorporatedinto a further structure. As an example, recent developments havefabricated display matrices on flexible substrates.

MEMS (microelectromechanical system) devices have also gained inpopularity in the electronics industry. Many types of MEMS devices havebeen developed for a myriad of applications, including MEMS sensorsconfigured to measure pressure variations. Due to manufacturingconstraints, however, the fabrication of MEMS devices has been relegatedthus far to standard substrates such as silicon substrates. Integrationof MEMS devices with displays and/or other devices fabricated onflexible substrates has thus been constrained.

Therefore, a need exists in the art to develop MEMS devices compatiblewith flexible substrates and methods to integrate the fabrication ofsuch MEMS devices along with other devices on flexible substrates.

BRIEF DESCRIPTION OF THE DRAWINGS

To facilitate further description of the embodiments, the followingdrawings are provided in which:

FIG. 1 illustrates a perspective view of a semiconductor devicecomprising a MEMS device according to a first embodiment;

FIG. 2 illustrates a cross-sectional view along a line 1-1 of thesemiconductor device of FIG. 1;

FIG. 3 illustrates a perspective view of a semiconductor devicecomprising a MEMS array having the MEMS device of FIGS. 1-2;

FIG. 4 illustrates a flowchart for a method for providing asemiconductor device;

FIG. 5 illustrates a cross-sectional view of a portion of a MEMS devicecomprising a flexible substrate and a first plate in accordance with themethod of FIG. 4;

FIG. 6 illustrates a cross-sectional view of a portion of the MEMSdevice of FIG. 5 further comprising a first dielectric;

FIG. 7 illustrates a cross-sectional view of a portion of the MEMSdevice of

FIG. 6 after a first part of the formation of a sacrificial structure;

FIG. 8 illustrates a cross-sectional view of a portion of the MEMSdevice of FIG. 7 after a second part of the formation of the sacrificialstructure;

FIG. 9 illustrates a cross-sectional view of a portion of the MEMSdevice of FIG. 8 after a first part of the formation of a sensormembrane;

FIG. 10 illustrates a cross-sectional view of a portion of the MEMSdevice of FIG. 9 after a second part of the formation of the sensormembrane;

FIG. 11 illustrates a cross-sectional view of a portion of the MEMSdevice of FIG. 10 after removal of the sacrificial layer; and

FIG. 12 illustrates a cross-sectional view of a semiconductor devicecomprising both the MEMS device of FIG. 11 and an electronic device12500 fabricated over the same flexible substrate.

For simplicity and clarity of illustration, the drawing figuresillustrate the general manner of construction, and descriptions anddetails of well-known features and techniques may be omitted to avoidunnecessarily obscuring the invention. Additionally, elements in thedrawing figures are not necessarily drawn to scale. For example, thedimensions of some of the elements in the figures may be exaggeratedrelative to other elements to help improve understanding of embodimentsof the present invention. The same reference numerals in differentfigures denote the same elements.

The terms “first,” “second,” “third,” “fourth,” and the like in thedescription and in the claims, if any, are used for distinguishingbetween similar elements and not necessarily for describing a particularsequential or chronological order. It is to be understood that the termsso used are interchangeable under appropriate circumstances such thatthe embodiments described herein are, for example, capable of operationin sequences other than those illustrated or otherwise described herein.Furthermore, the terms “include,” and “have,” and any variationsthereof, are intended to cover a non-exclusive inclusion, such that aprocess, method, system, article, device, or apparatus that comprises alist of elements is not necessarily limited to those elements, but mayinclude other elements not expressly listed or inherent to such process,method, system, article, device, or apparatus.

The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “over,”“under,” and the like in the description and in the claims, if any, areused for descriptive purposes and not necessarily for describingpermanent relative positions. It is to be understood that the terms soused are interchangeable under appropriate circumstances such that theembodiments of the invention described herein are, for example, capableof operation in other orientations than those illustrated or otherwisedescribed herein.

The terms “couple,” “coupled,” “couples,” “coupling,” and the likeshould be broadly understood and refer to connecting two or moreelements or signals, electrically, mechanically and/or otherwise. Two ormore electrical elements may be electrically coupled together, but notbe mechanically or otherwise coupled together; two or more mechanicalelements may be mechanically coupled together, but not be electricallyor otherwise coupled together; two or more electrical elements may bemechanically coupled together, but not be electrically or otherwisecoupled together. Coupling may be for any length of time, e.g.,permanent or semi-permanent or only for an instant.

“Electrical coupling” and the like should be broadly understood andinclude coupling involving any electrical signal, whether a powersignal, a data signal, and/or other types or combinations of electricalsignals. “Mechanical coupling” and the like should be broadly understoodand include mechanical coupling of all types.

The absence of the word “removably,” “removable,” and the like near theword “coupled,” and the like does not mean that the coupling, etc. inquestion is or is not removable.

DETAILED DESCRIPTION OF EXAMPLES OF EMBODIMENTS

In one embodiment, a semiconductor device comprises a flexible substrateand a MEMS device fabricated over the flexible substrate. In the same ora different embodiment, the semiconductor device can comprise anelectronic device fabricated over the substrate and electrically coupledto the MEMS device. In the same and other embodiments, the MEMS devicecan comprise an electrically conductive material located over theflexible substrate, a sensor membrane movably suspended over theelectrically conductive material, and a first dielectric located overthe electrically conductive material and under the sensor membrane.

In another embodiment, a method for providing a semiconductor device cancomprise providing a flexible substrate and forming a MEMS device overthe substrate. Forming the MEMS device can comprise providing anelectrically conductive layer over the substrate, providing a firstdielectric over the electrically conductive layer, providing asacrificial structure over the first dielectric, and providing a sensormembrane over the sacrificial structure. Other embodiments are describedand claimed herein.

Turning to the drawings, FIG. 1 illustrates a perspective view of asemiconductor device comprising MEMS device 120 in accordance with anembodiment of the present disclosure. FIG. 2 illustrates across-sectional view along a line 1-1 of MEMS device 120 of FIG. 1. MEMSdevice 120 is merely exemplary and is not limited to the embodimentspresented herein.

In the example of FIGS. 1-2, semiconductor device 100 comprises MEMSdevice 120 integrally fabricated over flexible semiconductor substrate110. In the same and other examples, substrate 110 (or substrate body210) can be a plastic substrate, and/or can comprise at least one of aflexible polyethylene naphthalate (PEN) material, such as that availablefrom Teijin DuPont Films of Tokyo, Japan, under the tradename planarized“Teonex® Q65,” a polyethylene terephthalate (PET) material, apolyethersulfone (PES) material, a polyimide, a polycarbonate, a cyclicolefin copolymer, and/or a liquid crystal polymer. In other examples,substrate 110 can comprise other materials such as a stainless steelmaterial, a silicon material, an iron nickel (FeNi) alloy material(e.g., FeNi, FeNi36, or Inver™; where Inver™ comprises an alloy of iron(64 percent (%)) and nickel (36%) (by weight) with some carbon andchromium), an iron nickel cobalt (FeNiCo) alloy material (e.g., Kovar™,where Kovar™ typically comprises 29% nickel, 17% cobalt, 0.2% silicon,0.3% manganese, and 53.5% iron (by weight)), a titanium material, atantalum material, a molybdenum material, an aluchrome material, and/oran aluminum material.

As seen in FIG. 2, semiconductor substrate 110 comprises planarizationlayer 111 between substrate body 210 of substrate 110 and MEMS device120 in the present example. In some examples, planarization layer 111can comprise a dielectric passivation material over substrate body 210,such as silicon nitride.

As illustrated in FIGS. 1-2, MEMS device 120 can be fabricated directlyon substrate 110, and can comprise electrically conductive material 220located over substrate 110, dielectric 230 located over electricallyconductive material 220, and sensor membrane 121 suspended overdielectric 230. Electrically conductive material 220 comprises ametallic layer in the present example, and can comprise a metallicmaterial such as molybdenum, tantalum, aluminum, tungsten, and/or goldin at least some embodiments. There can be some embodiments whereelectrically conductive material 220 can be referred to as a plate.Dielectric 230 comprises a dielectric layer in the present example, andcan comprise materials such as silicon nitride, silicon dioxide (SiO₂),and/or polyimide, in at least some embodiments.

In the present embodiment, membrane perimeter 1211 of sensor membrane121 is supported by wall structure 122 over dielectric 230. Wallstructure 122 comprises one or more dielectric layers deposited overdielectric 230 along sensor perimeter 150 of MEMS device 120 in thepresent example, and can comprise a silicon nitride material in at leastsome embodiments. As seen in FIG. 1, sensor perimeter 150 comprises acircular shape, and membrane perimeter 1211 of sensor membrane 121 isalso correspondingly circular. In the same or a different embodiment,sensor perimeter 150 and/or membrane perimeter 1211 can comprise aradius of between approximately 50 micrometers to approximately 250micrometers. In the example of FIGS. 1-2, sensor membrane 121 comprisesa radius of approximately 70 micrometers. Another example can comprise asensor membrane with a radius of approximately 200 micrometers. Therecan also be other embodiments where at least one of sensor perimeter 150and/or membrane perimeter 1211 can comprise non-circular shapes, such asoval or square shapes. With a circular shape, however, MEMS device 120can be more stable without needing a central support, as shown in FIG.2. Wall structure 122 also defines sacrificial compartment 270 betweensensor membrane 121 and dielectric 230. In the present example,sacrificial compartment 270 comprises an air gap.

As shown in FIGS. 1-2, sensor membrane 121 comprises one or moreopenings 123 leading to sacrificial compartment 270. In the presentembodiment, MEMS device 120 comprises 7 openings 123 in sensor membrane121, although other embodiments can comprise a different number ofopenings. For example, some implementations can comprise betweenapproximately 5 to 20 openings leading to the sacrificial compartment.In the present example, one or more of openings 123 of sensor membrane121 can measure approximately 12 micrometers by approximately 12micrometers. In other examples where the sensor membrane comprisesapproximately between 10 to 150 openings, one or more of such openingscan measure approximately 10-20 micrometers by approximately 10-20micrometers. There can be further examples with openings comprisingnon-square perimeters, but otherwise can be similar to openings 123. Inthe present and other embodiments, openings 123 can be employed duringthe formation of sacrificial compartment 270. The formation ofsacrificial compartment 270 will be further described below.

Sensor membrane 121 also comprises electrically conductive material 1212facing dielectric 230 in the present example, where electricallyconductive material 1212 can comprise a metallic material such asmolybdenum, aluminum, tantalum, tungsten, and/or gold. In the same orother examples, a layer of doped amorphous silicon can also comprisepart of electrically conductive material 1212 or be located adjacentthereto.

As seen in FIG. 2, electrically conductive material 1212 couples tosupport layer 1213 of sensor membrane 121, where support layer 1213 canbe deposited above electrically conductive material 1212 duringfabrication. In the present embodiment, perimeter 1211 of sensormembrane 121 comprises a perimeter of support layer 1213, and theperimeter of support layer 1213 anchors sensor membrane 121 to wallstructure 122 past a perimeter of electrically conductive material 1212.In some examples, support layer 1213 can comprise a silicon nitridematerial, a silicon oxynitride (SiO_(x)N_(y)) material, a silicondioxide (SiO₂) material, a passivation material, a siloxane-basedmaterial, an organosiloxane material, an organic siloxane-basedmaterial, and/or another dielectric material. In the same or otherexamples, support layer 1213 can comprise a PTS material such as thatavailable from Honeywell International, Inc. of Morristown, N.J., underthe name PTS-R.

In the same or a different example, support layer 1213 can comprise athickness of between approximately 2 micrometers to approximately 2.5micrometers. In the same or a different example, MEMS device 120 cancomprise a height of between approximately 2.5 micrometers toapproximately 3.5 micrometers over substrate 110.

In the present embodiment MEMS device 120 comprises a shock or pressuresensor, and is configured to sense variations in pressure by detectingchanges in capacitance between sensor membrane 121 and electricallyconductive material 220. In the same and other embodiments, electricallyconductive material 220 and electrically conductive material 1212 ofsensor membrane 121 can be considered as the plates of a capacitor,where the capacitance between the plates changes as sensor membrane 121moves or deforms, at least temporarily, relative to electricallyconductive material 220 as a result of the variations in pressure. Inthe same or other embodiments, when subject to shock waves and/orpressure changes, sensor membrane 121 can move or deform enough to movetoward and/or make contact with dielectric 230 over electricallyconductive material 220. In some embodiments, when in a steady state notsubject to pressure variations, MEMS device 120 can comprise acapacitance of between approximately 1.5 picofarads and approximately8.0 picofarads. In the same or different embodiments, MEMS device 120can comprise a capacitance of between approximately 1.89 picofarads andapproximately 7.8 picofarads. There can be embodiments where MEMS device120 can sense pressure changes or shocks of between approximately 15kilopascals (kPa) and 60 kPa. For example, where sensor membranes 121comprises a radius of 70 micrometers, MEMs device 120 may be configuredto sense pressure changes of approximately 50 kPa. In other exampleswith sensor membranes comprising a radius of 200 micrometers, pressurechanges of approximately 20 kPa may be sensed.

FIG. 3 illustrates a perspective view of semiconductor device 300comprising MEMS array 320. In the embodiment of FIG. 3, MEMS array 320comprises one or more MEMS sensors coupled together, including MEMSdevice 120 of FIGS. 1-2 as fabricated over substrate 110. Although theMEMS sensors of array 320 comprise the same diameter in the presentexamples, there can be examples where the MEMS array can comprise one ormore MEMS sensors with a first diameter and one or more MEMS sensorswith a different diameter and/or a different shape. In the present andother embodiments, semiconductor device 100 can comprise one or moreelectronic devices fabricated over substrate 110 different than MEMSdevice 120. For example, as shown in FIG. 3, one or more electronicdevices 310, such as electronic device 311, can also be fabricated oversubstrate 110 and electrically coupled to MEMS device 120.

In the same or a different embodiment, MEMS device 120 and the otherMEMS sensors of MEMS array 320 can be fabricated simultaneously oversubstrate 110 with electronic devices 310 using the same semiconductorprocess flow, or a modification of the semiconductor process flow, usedfor electronic devices 310, or vice versa. For example, electronicdevice 311 can comprise at least one transistor (not shown), andelectrically conductive material 220 of MEMS device 120 (FIG. 2) cancomprise a gate material used for a gate electrode of the at least onetransistor of electronic device 311. In the same or a different example,dielectric 230 of MEMS device 120 (FIG. 2) can comprise a gatedielectric material used for a gate dielectric of the at least onetransistor of electronic device 311.

Semiconductor device 300 can be implemented as a shock sensor and/or todetect pressure variations, and in the present and other examples, twoor more of the MEMS sensors of MEMS array 320 can be coupled together inparallel to enhance the sensitivity of semiconductor device 300. Theparallel coupling of the MEMS sensors of MEMS array 320 can increase thetotal capacitance of semiconductor device 300 and can help to minimizefalse readings by adding a level of redundancy to semiconductor device300. In the same or other examples, such an arrangement can help toovercome false positives caused by random and/or faulty MEMs sensors.

In the present example, electronic device 311 represents a capacitancemeasurement circuit configured to measure and/or process the shock orpressure variations detected by MEMS array 310. In the same or adifferent example, semiconductor device 300 can comprise otherelectronic devices 310 such as display circuits (not shown) integrallyfabricated over substrate 110. In such embodiments, the display circuitscan comprise display elements such as pixels (picture elements) of adisplay, and can be electrically coupled to MEMS array 320 and/or to thecapacitance measurement circuit of electronic device 311.

In the present and other implementations, semiconductor device 300 canintegrate MEMS array 320 and other electronic devices 310 onto a singleflexible substrate suitable for sensing and/or measuring shock orpressure variations, processing information out of the measurements, anddisplaying the information on the single flexible substrate. In the sameor different embodiments, semiconductor device 300 can be configured toprocess blast dosimetry information measured at least partially via MEMSdevice 120 and/or to keep record of, for example, a number and/ormagnitude of nearby explosions or shockwaves that a soldier has beenexposed to during a period of time. In such examples, semiconductordevice 300 can be attached to the soldier's gear and/or to the body ofthe soldier at predetermined locations, including locations expected tobe exposed to peak shockwaves. As an example, semiconductor device 300can be attached to a helmet and/or near the top back of the skull of thesoldier. In the same or other examples, semiconductor device 300 can beattached with or as an adhesive bandage.

Moving along, FIG. 4 illustrates a flowchart for a method 400 that canbe used for providing a semiconductor device. In the same or differentembodiments, method 400 can be considered a method of manufacturing aMEMS device, such as MEMS device 120 (FIGS. 1-3), over a flexiblesubstrate. Method 400 is merely exemplary and is not limited to theembodiments presented herein. Method 400 can be employed in manydifferent embodiments or examples not specifically depicted or describedherein.

Method 400 includes a procedure 410 of providing a substrate. FIG. 5illustrates a cross-sectional view of a portion of MEMS device 500comprising substrate 510, where substrate 510 can be similar to thesubstrate of procedure 410 and/or to substrate 110 (FIGS. 1-2) in someembodiments. In the same or different embodiments, procedure 410 ofmethod 400 can include providing a flexible substrate. In many examples,the flexible substrate can be a plastic substrate. For example, in theembodiment of FIG. 5, body 512 of substrate 510 can be similar tosubstrate body 210 in FIG. 2, and can comprise a flexible polyethylenenaphthalate (PEN) material, such as that available from Teijin DuPontFilms of Tokyo, Japan, sold under the tradename planarized “Teonex®Q65.” In other embodiments, the substrate of procedure 410 can comprisea flexible substrate comprising polyethylene terephthalate (PET),polyethersulfone (PES), polyimide, polycarbonate, cyclic olefincopolymer, and/or liquid crystal polymer. The thickness of the substrateof method 400 can be in the range of approximately 25 micrometers toapproximately 300 micrometers in some embodiments. In the same ordifferent embodiments, the thickness of the substrate can be in therange of approximately 100 micrometers to approximately 200 micrometers.

In some examples, procedure 410 can further comprise providing aplanarized surface over the substrate. In the example of FIG. 5, theplanarized surface of procedure 410 can be formed by planarization layer511, where layer 511 can comprise a passivation layer at the top ofsubstrate 510. In some embodiments, planarization layer 511 can comprisea dielectric material such as silicon nitride, and can have a thicknessof approximately 3000 Angstroms. Layer 511 can be similar toplanarization layer 111 in FIG. 2.

In a different example, procedure 410 can include providing a stainlesssteel flexible substrate. In still further examples, the substrate ofprocedure 410 can include silicon, iron nickel (FeNi) alloys (e.g.,FeNi, FeNi36, or Inver™; where Inver™ comprises an alloy of iron (64%)and nickel (36%) (by weight) with some carbon and chromium), iron nickelcobalt (FeNiCo) alloys (e.g., Kovar™, where Kovar™ typically comprises29% nickel, 17% cobalt, 0.2% silicon, 0.3% manganese, and 53.5% iron (byweight)), titanium, tantalum, molybdenum, aluchrome, and/or aluminum.

In the same or different embodiments, the substrate of procedure 410 canbe coupled to a carrier (not shown) to provide rigidity and/or tosupport the substrate. In various embodiments, the carrier includes atleast one of the following: alumina (Al₂O₃), silicon, glass, steel,sapphire, barium borosilicate, soda lime silicate, alkalai silicates, orother materials. The carrier can be coupled to the substrate using anadhesive or by other means. For example, the carrier could comprisesapphire with a thickness between approximately 0.7 millimeters (mm) andapproximately 1.1 mm. The carrier could also comprise 96% alumina with athickness between approximately 0.7 mm and approximately 1.1 mm. In adifferent embodiment, the thickness of the 96% alumina can beapproximately 2.0 mm. In another example, the carrier could comprisesingle crystal silicon with a thickness of at least approximately 0.65mm. In some examples, the carrier is slightly larger than the substrate.

The substrate of procedure 410 can be cleaned in some examples to removeany particles on the substrate. In some embodiments, the substrate canbe cleaned to remove any adhesives on the substrate. For example, if thesubstrate is stainless steel, the substrate can be washed with hexanesfor approximately twenty seconds while spinning at approximately 1,000rpm (revolutions per minute). In some examples, the edge of thesubstrate can be sprayed with hexanes for the last ten seconds.Afterwards, the substrate can be spun at approximately 3,000 rpm forapproximately twenty seconds to dry the substrate. In some examples, thesubstrate can be baked for approximately sixty seconds at approximately105 degrees Celsius (° C.) to further dry the substrate.

To remove large particles from the substrate, the substrate of procedure410 can be scrubbed. For example, if the substrate is stainless steel,the substrate can be scrubbed with soap and water (e.g., 40 milliliters(mL) of Alconox Detergent 8 mixed with one liter of water) using asponge. Alconox Detergent 8 is manufactured by Alconox, Inc. of WhitePlains, N.Y. Organics can also be removed from the substrate by ashingin some examples. For example, if the substrate is stainless steel, thesubstrate can be ashed for approximately ninety minutes in an oxygen(O₂) environment at a pressure of approximately 1,200 milliTorr.

Continuing with method 400, procedure 420 comprises forming a first MEMSdevice over the substrate of procedure 410. In some embodiments, thefirst MEMS device of procedure 420 can be similar to MEMS device 120from FIGS. 1-3). In the same or different embodiments, procedure 420 cancomprise several subparts such as such as procedures 421-425.

In the present example of FIG. 4, procedure 421 comprises providing anelectrically conductive layer over the substrate of procedure 410. Insome embodiments, the electrically conductive layer can be referred toas a gate layer or as a first plate. In the same or other embodiments,the electrically conductive layer of procedure 421 can be similar toplate 520 of MEMS device 500 in FIG. 5. In turn, plate 520 can besimilar to electrically conductive material 220 of semiconductor device100 (FIG. 2). In the same or a different embodiments, plate 520 can bedeposited over substrate 510 and then patterned to a desired form.

Procedure 422 of method 400 comprises providing a first dielectric overthe electrically conductive layer of procedure 421. FIG. 6 illustrates across-sectional view of a portion of MEMS device 500 comprisingdielectric 630, where dielectric 630 can be similar to the firstdielectric of procedure 420 and/or to dielectric 230 (FIG. 2) in someembodiments. Dielectric 630 is deposited over planarization layer 511 ofsubstrate 510 in the present example to a thickness of approximately3000 Angstroms.

Procedure 423 of method 400 comprises providing a sacrificial structureover the first dielectric of procedure 422. In some examples, thesacrificial structure can be used to form sacrificial compartment 270(FIG. 2) described for MEMS device 120 above. In the same or a differentexample, the sacrificial structure can be similar to sacrificialstructure 770 as described in FIGS. 7-8. FIG. 7 illustrates across-sectional view of a portion of MEMS device 500 after a first partof the formation of sacrificial structure 770. FIG. 8 illustrates across-sectional view of a portion of MEMS device 500 after a second partof the formation of sacrificial structure 770.

In the present example of method 400, part of procedure 423 comprisesproviding a sacrificial layer over the first dielectric of procedure422. In the example of FIG. 7, sacrificial layer 771 deposited overdielectric 630 can be similar to the sacrificial layer of procedure 423of method 400. In some examples, sacrificial layer 771 can comprise anamorphous silicon channel material. In the same or other examples, thesacrificial layer can be deposited over dielectric 630 to a thickness ofapproximately 0.08 micrometers. In the present example, sacrificialstructure 770 also comprises dielectric layer 772 deposited oversacrificial layer 771, where dielectric layer 772 can comprise apatterned silicon nitride intermetal dielectric (IMD) layer having athickness of approximately 0.10 micrometers in some examples. In otherembodiments, sacrificial structure 700 can comprise a single layer.

In the present example, part of procedure 423 of method 400 can alsocomprise providing a compartment wall at a perimeter of the sacrificiallayer and over the first dielectric, where the compartment wall forprocedure 423 can be similar to wall structure 122 of semiconductordevice 100 (FIGS. 1-2). In the same or different examples, now referringto FIG. 8, compartment wall 822 can correspond to the compartment wallfor procedure 423 as formed by dielectric layer 873. In the presentexample, dielectric layer 873 comprises a patterned approximately 0.10micrometer thick silicon nitride layer. In the same or other examples,dielectric layer 873 can comprise a passivation material. There can alsobe other examples where dielectric layer 873 can comprise otherdielectric materials and/or IMD layer.

As seen in FIG. 8, compartment wall 822 can be formed by providing oneor more dielectric layers, such as dielectric layers 772 and 873, oversacrificial layer 771. In other examples, dielectric layer 772 can beomitted from compartment wall 822 such that compartment wall 822 wouldonly comprise a single dielectric layer comprising the space occupied bydielectric layers 772 and 873 in FIG. 8. A perimeter of dielectric layer873 contacts dielectric 630 in the present example past a perimeter ofsacrificial layer 771 and dielectric layer 772. As a result, compartmentwall 822 bounds the perimeter of sacrificial layer 771 and dielectriclayer 772 in the present example.

Once placed over sacrificial layer 771, the one or more dielectriclayers described above can be patterned to remove portions thereof oversacrificial layer 771 and thereby further define compartment wall 822.For example, FIG. 8 presents dielectric layers 873 and 772 after beingetched to expose at least part of sacrificial layer 771.

Continuing with method 400, procedure 424 comprises providing a sensormembrane over the sacrificial structure of procedure 423. In someexamples, the sensor membrane of procedure 424 can be similar to sensormembrane 121 of MEMS device 120 (FIGS. 1-2). In the same or differentexamples, the sensor membrane of procedure 424 and/or sensor membrane121 can be similar to sensor membrane 921 as illustrated in FIGS. 9-11,and/or can comprise a substantially circular perimeter.

In the present example, part of procedure 424 comprises providing asecond electrically conductive layer over the sacrificial structure ofprocedure 423. FIG. 9 illustrates a cross-sectional view of a portion ofMEMS device 500 after a first part of the formation of sensor membrane921. In the embodiment of FIG. 9, the second electrically conductivelayer described for procedure 424 can be similar to plate 9212 of sensormembrane 921 over sacrificial structure 770. In the same or a differentembodiment, the second electrically conductive layer of procedure 424and/or plate 9212 can be similar to electrically conductive material1212 described above for MEMS device 120 (FIG. 2). In some examples,plate 9212 can have a thickness of approximately 0.20 micrometers. Inthe same or different examples, plate 9212 can comprise at least one ofan aluminum material, a molybdenum material, a tungsten material, a goldmaterial and/or a tantalum material. There may be embodiments whereplate 9212 can comprise a stack of more than one material.

As seen in FIG. 9, one or more openings 923 can be etched through plate9212 to expose one or more portions of sacrificial structure 770 and/orof sacrificial layer 771 in at least some embodiments. Openings 923 canbe similar, for example, to openings 123 through membrane 121 of MEMSdevice 120 as described above for FIGS. 1-2. In the same or differentexamples, plate 9212 can be etched in one in-situ etching procedure withdielectric layer 873 and/or sacrificial layer 771 acting as etch stoplayers. In some examples, plate 9212 can be etched using an AMAT 8330,manufactured by Applied Material, Inc. of Santa Clara, Calif. Aperimeter of plate 9212 can extend beyond a perimeter of plate 520, asillustrated in FIG. 9.

Another part of procedure 424 of method 400 can comprise providing astructural layer over the second electrically conductive layer. As anexample, FIG. 10 illustrates a cross-sectional view of a portion of MEMSdevice 500 after a second part of the formation of sensor membrane 921.In the embodiment of FIG. 10, the structural layer described forprocedure 424 can be similar to structural layer 10211 of sensormembrane 921 over plate 9212. In the same or a different embodiment, thestructural layer of procedure 424 and/or structural layer 10211 can besimilar to support layer 1213 described above for MEMS device 120 (FIG.2), and can comprise similar materials. There may be embodiments wherestructural layer 10211 can comprise a stack of more than one material.In the present example of FIG. 10, a perimeter of structural layer 10211is shown coupled with a perimeter of sacrificial structure 770 past aperimeter of plate 9212. As a result, the perimeter of structural layer10211 contacts with dielectric layer 873 at the perimeter of compartmentwall 822 and bounds the perimeter of plate 9212 in the present example.As seen in FIG. 10, one or more openings 1023 can be etched throughstructural layer 10211 to expose one or more portions of sacrificialstructure 770 and/or of sacrificial layer 771 in at least someembodiments. Openings 1023 can be similar to, and substantially alignedwith, openings 923 as etched through plate 9212, and can also be similarto openings 123 through membrane 121 of MEMS device 120 as describedabove for FIGS. 1-2. In some examples, openings 1023 can be plasmaetched. In the same of different embodiments, openings 1023 can beetched with a fluorine-based etchant. In some examples, the etchant canbe trifluoromethane (CHF₃), sulfur hexafluoride (SF₆), or otherfluorine-based etchants. In some embodiments, openings 1023 can beformed before openings 923, and after forming openings 1023, theremainder of structural layer 10211 can be used as a self-aligned etchmask for openings 923.

There can be examples, including those where the substrate of procedure410 comprises a plastic substrate, where the different procedures ofmethod 400 to form the first MEMS device are carried out at temperaturesnot exceeding approximately 190 degrees Celsius. In such examples, thelow temperature at which the MEMS device of procedure 420 is fabricatedcan assist in preventing heat-related damage to the susbstrate ofprocedure 410 and/or to elements of the MEMS device of procedure 420.

Continuing with method 400, procedure 425 comprises removing thesacrificial layer described above for procedure 423 via one or moreopenings of the sensor membrane of procedure 424. In some examples, asacrificial compartment similar to sacrificial compartment 270 of MEMSdevice 120 (FIG. 2) remains between the sensor membrane of procedure 424and the first dielectric of procedure 422 after the sacrificial layer isremoved in procedure 425. FIG. 11 illustrates a cross-sectional view ofa portion of MEMS device 500 after removal of sacrificial layer 771 fromsacrificial compartment 1170 between sensor membrane 921 and dielectric630 in accordance with an implementation of procedure 425 of method 400.In the example of FIG. 11, sacrificial layer 771 has been removed viaetching through openings 1023 of sensor membrane 921 to release sensormembrane 921. In some examples, the etching through openings 1023 can beperformed using a dry etch process. In the same or a different example,the etching through openings 1023 can comprise the use of a xenondifluoride (XeF₂) reactant or another gaseous reactant. The use of a dryetchant eliminates the problem of stiction when a wet etchant is used.In the same or a different example, the reactant used for etchingsacrificial layer 771 comprises enough selectivity to etch only atsacrificial layer 771 without etching or at least without substantiallyetching sacrificial structure 770 or any other element boundingsacrificial compartment 1170, including plate 9212, dielectric 630,compartment wall 822, dielectric layer 873, structural layer 10211, ordielectric layer 772. In the same or a different example, no separatemasking is needed prior to carrying out the etch of sacrificial layer771.

In some examples, method 400 can comprise procedure 440, comprisingforming over the substrate a second MEMS device electrically coupled inparallel with the first MEMS device of procedure 420. In some examples,the second MEMS device can be similar to the first MEMS device and/orcan be manufactured using the same semiconductor process flow. In thesame or a different example, the first and second MEMS devices of method400 can be coupled together as described above with respect to FIG. 3for the MEMS sensors of MEMS array 320. In the same or a differentexample, the second MEMS device of procedure 440 can comprise a sensormembrane with a diameter and/or a perimeter different than a diameterand/or a perimeter of the sensor membrane provided in procedure 424 forthe first MEMS device of procedure 420.

There can be some examples where method 400 also can comprise procedure450, comprising forming over the substrate an electronic deviceelectrically coupled to the MEMS device of procedure 420. In the same ora different example, the electronic device can be similar to one ofelectronic devices 310 described above for FIG. 3, and/or could compriseat least part of a display element and/or a capacitance measurementcircuit.

In some embodiments, method 400 can be implemented such that the MEMSdevice of procedure 420 is fabricated pursuant to a semiconductorprocess flow for the electronic device of procedure 450 over theflexible substrate of procedure 410, or a modification of suchsemiconductor process flow. As an example, FIG. 12 illustrates across-sectional view of semiconductor device 12000 comprising both MEMSdevice 500 and electronic device 12500 fabricated over flexiblesubstrate 510. In some examples, electronic device 12500 can correspondto at least part of the electronic device of procedure 450. In the sameor a different examples, the part of the electronic device comprises atransistor, and in particular, a thin film transistor.

As can be seen in FIG. 12, MEMS device 500 shares substrate 510,including body 512 and planarization layer 511, with electronic device12500. Other elements of MEMS device 500 can be fabricated with layersused to fabricate corresponding elements of electronic device 12500. Forexample, plate 520 of MEMS device 500 can be fabricated out of the samelayer or electrically conductive material used to fabricate gateelectrode 12520 of electronic device 12500. As a result, the electricalconductive material of plate 520 and the gate electrode of electronicdevice 12500 can be provided simultaneously during the fabrication ofsemiconductor device 12000.

In similar fashion, dielectric 630 of MEMS device 500 can be fabricatedout of the same layer of material used to fabricate gate dielectric12630 of electronic device 12500. As a result, dielectric 630 and gatedielectric 12630 can be provided simultaneously during fabrication ofsemiconductor device 12000.

Plate 9212 of sensor membrane 921 if MEMS device 500 can be fabricatedout of the same layer or layers of electrically conductive material assource/drain conductive layer 129212 of electronic device 12500. As aresult, plate 9212 and source/drain conductive layer 129212 can beprovided simultaneously during fabrication of semiconductor device12000.

Structural layer 10211 of sensor membrane 921 of MEMS device 500 can befabricated out of the same layer or layers of material used to fabricateplanarization layer 1210211 of electronic device 12500. As a result,structural layer 10211 and planarization layer 1210211 can be providedsimultaneously during fabrication of semiconductor device 12000.

Other elements of MEMS device 500 can be similarly fabricated based onlayers used to fabricate elements of electronic device 12500. Forexample, although sacrificial layer 771 is already removed from MEMSdevice 500 in FIG. 12, in accordance with procedure 425 of method 400,sacrificial layer 771 of MEMS device 500 can be fabricated out of thesame layer of channel material used to fabricate channel 12771 ofelectronic device 12500. Similarly, dielectric layer 772 of MEMS device500 can be fabricated out of the same layer of material used tofabricate IMD layer 12772 of electronic device 12500. Dielectric layer873 of MEMS device 500 can be fabricated out of the same layer ofmaterial used to fabricate passivation layer 12873 of electronic device12500.

In the example of FIG. 12, layer 12020 is located over planarizationlayer 1210211 of electronic device 12500, and layer 12010 is locatedover layer 12020 of electronic device 12500. In some examples, layer12020 can comprise an indium-tin-oxide material, and/or layer 12010 cancomprise silicon nitride or other dielectric material configured tocreate an overglass protection layer. Although layers 12010 and 12020are not needed in the present example for MEMS device 500, MEMS device500 is still compatible with the semiconductor process for electronicdevice 12500. For example, layers 12010 and 12020 can be formed andpatterned over structural layer 10211 before the removal of sacrificiallayer 771.

In some examples, one or more of the different procedures of method 400can be combined into a single step or performed simultaneously, and/orthe sequence of such procedures can be changed. For example, procedure450 could be performed before procedure 440 in some examples. In otherexamples, the first MEMS device of procedure 420, the second MEMS deviceof procedure 440, and the electronic device of procedure 450 can befabricated simultaneously and/or combined into a single step. There canalso be examples where method 400 can comprise further or differentprocedures. As an example, a procedure could be added after procedure450 to form a second electronic device over the substrate of procedure410. In such an example, the electronic device of procedure 450 couldform part of a capacitance measurement circuit, and the electronicdevice of procedure 460 could form part of a display circuit for thesemiconductor device of method 400. Other variations can be implementedfor method 400 without departing from the scope of the presentdisclosure.

Although the embedded MEMS sensors and related methods herein have beendescribed with reference to specific embodiments, various changes may bemade without departing from the spirit or scope of the presentdisclosure. For example, even though openings 123 of MEMS device 120have been presented as square-shaped, there can be embodiments withsimilar openings comprising other geometrical perimeters. Additionalexamples of such changes have been given in the foregoing description.Accordingly, the disclosure of embodiments herein is intended to beillustrative of the scope of the invention and is not intended to belimiting. It is intended that the scope of this application shall belimited only to the extent required by the appended claims. The embeddedMEMS sensors and related methods discussed herein may be implemented ina variety of embodiments, and the foregoing discussion of certain ofthese embodiments does not necessarily represent a complete descriptionof all possible embodiments. Rather, the detailed description of thedrawings, and the drawings themselves, disclose at least one preferredembodiment, and may disclose alternative embodiments.

Although the invention has been described with reference to specificembodiments, it will be understood by those skilled in the art thatvarious changes may be made without departing from the spirit or scopeof the invention. Accordingly, the disclosure of embodiments of theinvention is intended to be illustrative of the scope of the inventionand is not intended to be limiting. It is intended that the scope of theinvention shall be limited only to the extent required by the appendedclaims. For example, to one of ordinary skill in the art, it will bereadily apparent that any of the procedures, processes, and/oractivities of method 400 (FIG. 4) may be comprised of many differentprocedures, processes, and activities and be performed by many differentmodules, in many different orders, that any element of FIGS. 1-12 may bemodified, and that the foregoing discussion of certain of theseembodiments does not necessarily represent a complete description of allpossible embodiments.

All elements claimed in any particular claim are essential to theembodiment claimed in that particular claim. Consequently, replacementof one or more claimed elements constitutes reconstruction and notrepair. Additionally, benefits, other advantages, and solutions toproblems have been described with regard to specific embodiments. Thebenefits, advantages, solutions to problems, and any element or elementsthat may cause any benefit, advantage, or solution to occur or becomemore pronounced, however, are not to be construed as critical, required,or essential features or elements of any or all of the claims, unlesssuch benefits, advantages, solutions, or elements are expressly statedin such claim.

Moreover, embodiments and limitations disclosed herein are not dedicatedto the public under the doctrine of dedication if the embodiments and/orlimitations: (1) are not expressly claimed in the claims; and (2) are orare potentially equivalents of express elements and/or limitations inthe claims under the doctrine of equivalents.

What is claimed is:
 1. A semiconductor device comprising: a flexiblesubstrate; and a MEMS device fabricated over the flexible surface;wherein: the MEMS device comprises: an electrically conductive materiallocated over the flexible substrate; a sensor membrane movably suspendedover the electrically conductive material; a first dielectric locatedover the electrically conductive material and under the sensor membrane;and a wall structure coupled to the first dielectric; and the sensormembrane is suspended by the wall structure over the electricallyconductive material.
 2. The semiconductor device of claim 1 furthercomprising at least one of: a planarization layer between the flexiblesubstrate and the MEMS device; an electronic device fabricated over theflexible substrate and electrically coupled to the MEMS device; or twoor more MEMS sensors electrically coupled in parallel with each other,wherein one of the two or more MEMS sensors comprises the MEMS device.3. The semiconductor device of claim 2 wherein: when the semiconductordevice comprises the electronic device, at least one of: the electronicdevice comprises at least one of a display element or a capacitancemeasurement circuit; or the electronic device is configured to processblast dosimetry information measured via the MEMS device.
 4. Thesemiconductor device of claim 1 wherein: the flexible substratecomprises at least one of: a PEN material, a PET material, a PESmaterial, a polyimide, a polycarbonate, a cyclic olefin copolymer, aliquid crystal polymer, a stainless steel material, a FeNi alloymaterial, a FeNiCo alloy material, a titanium material, a tantalummaterial, a molybdenum material, an aluchrome material, or an aluminummaterial.
 5. The semiconductor device of claim 1 wherein at least oneof: the electrically conductive material comprises at least one ofmolybdenum, tantalum, aluminum, tungsten, or gold; the sensor membraneis configured to move toward the first dielectric when deformed by atleast one of a shock wave or a pressure change; or the sensor membraneis substantially circular.
 6. The semiconductor device of claim 1wherein: the MEMS device further comprises a compartment between theelectrically conductive material and the sensor membrane.
 7. Thesemiconductor device of claim 6 wherein at least one of: the sensormembrane comprises between approximately 5 openings to approximately 20openings into the compartment; or the compartment defines an air gapbetween the electrically conductive material and the sensor membrane. 8.The semiconductor device of claim 7 wherein: the sensor membranecomprises: a second electrically conductive material facing the firstdielectric; and a support layer located over the second electricallyconductive material and anchored at a perimeter of the sensor membrane.9. The semiconductor device of claim 8 wherein at least one of: thesecond electrically conductive material comprises at least one ofaluminum, tantalum, molybdenum, tungsten, or gold; the support layercomprises at least one of a silicon nitride material, a siliconoxynitride material, a silicon dioxide material, a passivation material,a siloxane-based material, an organosiloxane material, an organicsiloxane-based material, or a PTS material; or the support layercomprises a thickness of between approximately 2 micrometers toapproximately 2.5 micrometers.
 10. The semiconductor device of claim 1wherein: the wall structure comprises one or more dielectric layerslocated over the first dielectric along a sensor perimeter of the MEMSdevice.
 11. The semiconductor device of claim 1 further comprising atleast one of: a first electronic device fabricated over the flexiblesubstrate and electrically coupled to the MEMS device, wherein the firstelectronic device comprises at least one first transistor and theelectrically conductive material comprises a gate electrode materialused for a gate electrode of the at least one first transistor of thefirst electronic device; or a second electronic device fabricated overthe flexible substrate and electrically coupled to the MEMS device,wherein the second electronic device comprises at least one secondtransistor and the first dielectric comprises a gate dielectric materialused for a gate dielectric of the at least one second transistor of thesecond electronic device.
 12. A semiconductor device comprising: aflexible substrate; and a MEMS device fabricated over the flexiblesurface; wherein at least one of: the MEMS device comprises a circularperimeter with a radius of between approximately 50 micrometers toapproximately 250 micrometers; the MEMS device comprises a height ofbetween approximately 2.5 micrometers to approximately 3.5 micrometers;or the MEMS device comprises a steady state capacitance of betweenapproximately 1.5 picofarads to approximately 8.0 picofarads.
 13. Amethod comprising: providing a flexible substrate; and fabricating afirst MEMS device over the flexible substrate; wherein: fabricating thefirst MEMS device comprises: providing an electrically conductivematerial layer located over the flexible substrate; providing a sensormembrane configured to be movably suspended over the electricallyconductive material layer; providing a first dielectric located over theelectrically conductive material layer and under the sensor membrane;and providing a wall structure coupled to the first dielectric; and thesensor membrane is configured to be suspended by the wall structure overthe electrically conductive material layer.
 14. The method of claim 13,wherein: fabricating the first MEMS device comprises: providing asacrificial structure over the electrically conductive material layer;and providing the sensor membrane over the sacrificial structure. 15.The method of claim 14 wherein at least one of: providing the flexiblesubstrate comprises providing the flexible substrate to comprise atleast one of a PEN material, a PET material, a PES material, apolyimide, a polycarbonate, a cyclic olefin copolymer, or a liquidcrystal polymer; the sacrificial structure comprises an amorphoussilicon material; providing the sensor membrane comprises providing thesensor membrane to comprise a substantially circular perimeter;fabricating the first MEMS device comprises forming the first MEMSdevice at temperatures not exceeding approximately 190 degrees Celsius;or fabricating the first MEMS device further comprises providing thefirst dielectric between the electrically conductive material layer andthe sacrificial structure.
 16. The method of claim 14 wherein: providingthe sacrificial structure comprises: providing a sacrificial layer overthe electrically conductive material layer.
 17. The method of claim 16wherein: providing the sacrificial structure comprises providing acompartment wall of the wall structure at a perimeter of the sacrificiallayer and over the electrically conductive material layer, thecompartment wall comprising one or more dielectric layers; providing thecompartment wall comprises providing a perimeter of at least one of theone or more dielectric layers of the compartment wall to couple with thefirst MEMS device past a perimeter of the sacrificial layer; and the oneor more dielectric layers over the sacrificial layer comprise at leastone of an intermetal dielectric material, a passivation material, or asilicon nitride material.
 18. The method of claim 16 further comprising:etching one or more openings through the sensor membrane to expose oneor more portions of the sacrificial layer; and removing the sacrificiallayer via the one or more openings of the sensor membrane.
 19. Themethod of claim 18 wherein: removing the sacrificial layer comprises dryetching the sacrificial layer through the one or more openings of thesensor membrane; and dry etching the sacrificial layer comprises usingat least one of a dry etch reactant, a gaseous reactant, or an XeF₂reactant.
 20. The method of claim 14 wherein: providing the sensormembrane comprises: providing a second electrically conductive materiallayer over the sacrificial structure; and providing a structural layerover the second electrically conductive material layer.
 21. The methodof claim 20 wherein at least one of: providing the structural layercomprises providing a perimeter of the structural layer to couple with aperimeter of the sacrificial structure past a perimeter of the secondelectrically conductive material layer; providing the sensor membranefurther comprises etching one or more openings through the secondelectrically conductive material layer to expose one or more portions ofthe sacrificial structure prior to providing the structural layer; thesecond electrically conductive material layer comprises at least one ofan aluminum material, a tantalum material, a molybdenum material, atungsten material, or a gold material; the structural layer comprises atleast one of a silicon nitride material, a silicon oxynitride material,a silicon dioxide material, a passivation material, a siloxane-basedmaterial, an organosiloxane material, an organic siloxane-basedmaterial, or a PTS material; or providing the sensor membrane furthercomprises etching one or more openings through the structural layer toexpose at least a portion of the sacrificial structure.
 22. The methodof claim 14 further comprising: forming over the flexible substrate anelectronic device electrically coupled to the first MEMS device; whereinthe electronic device comprises at least one of: a display element; or acapacitance measurement circuit.
 23. The method of claim 22 wherein atleast one of: the first MEMS device is fabricated pursuant to at leastone of: (1) a semiconductor process flow for the electronic device or(2) a modification of the semiconductor process flow for the electronicdevice; providing the electrically conductive material layer comprisessimultaneously providing the electrically conductive material layer anda gate electrode for a transistor of the electronic device; providingthe sensor membrane comprises providing at least a portion of the sensormembrane simultaneously with a channel material of a transistor of theelectronic device; or forming the electronic device comprises providinga gate dielectric of a transistor of the electronic devicesimultaneously with a dielectric of the first MEMS device.